<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>index05.html</title>
    <style>
        ul::before{
            content: "这是一个无序列表";
            color: red;
            font-size: 20px;
        }
        ul::after{
            content: "我是后面的内容";
            color: green;
            font-size: 20px;
        }

        h3::before{
            content: "";
            padding-left: 5px;
            background: red;
        }

    </style>
</head>
<body>
    <ul>
        <li>hello world</li>
        <li>hello world</li>
        <li>hello world</li>
    </ul>
    <h3>这是一个有序列表</h3>
</body>
</html>